Blue Hole

Blue Hole is a large circular submarine sinkhole with a coral-rimmed, nearly vertical wall that plunges to about 110–120 m and contains a narrow tunnel known as the Arch at roughly 52 m. The site’s sinkhole topography, steep drop-offs and dramatic wall diving make it a renowned and technically demanding dive destination where many divers explore the outer reef wall and upper coral outcrops. The dive is done from a small beach shore entry; common routes include descending the northern chimney called "The Bells" to about 28–30 m, drifting or swimming along the southward reef wall, and using the shallow sandy plateau or "saddle" at about 7–10 m for stops. Water temperatures are typically in the mid-20°C and visibility often ranges 20–40 m. The outer reef usually protects the hole from strong currents and waters inside are generally calm, though a gentle counter-current or strong flows can occur in the Arch tunnel. Significant hazards include the Arch and tunnel at 52 m being an overhead environment beyond recreational limits, risks of nitrogen narcosis and oxygen toxicity at depth, and a history of over one hundred fatalities; diving here requires Advanced Open Water or technical training, strict depth and gas management, use of safety lines, adherence to local rules, and awareness of park fees and typical 08:00–16:00 diving windows.